Artisan Naturals, soft or medium?

Hi there.We are very close to pressing 'buy' on an Artisan Naturals super king from you, but are a bit stuck on the firmness issue, as my partner and I are right on the border of soft / medium.We are both pretty lean - I am 6ft and weigh just under 11 stone, and she is 5ft9 and 9.5 stone. Personally I prefer the idea of going for a medium tension, seeing how we get on, then getting a topper if we absolutely need to? However I just wondered if you had any thoughts about that particular mattress, ie. Does it have a slightly softer or harder natural characteristic to it?We don't yet know whether we'll have a solid or slatted bed base, as that is also on the list... Currently we have our (very old and sagging ikea) mattress on the floor which isn't ideal but is actually quite comfortable! We will probably buy a simple slatted base and add a layer of MDF.Thanks in advance.